Infrared sensors are advantageous in many applications. Some infrared sensors are capable of detecting the heat emitted from an object, such that an object may be viewed by a human via the infrared sensor even if there is little or no visible light incident upon the object. For example, infrared sensors are utilized in night-vision technologies, such as in night-vision goggles to view people and objects at night, in satellite sensors to capture images of portions of the earth at night, and in aircraft sensors to view other aircraft or other objects at night, to name a few. In addition, infrared sensors are not as affected by smoke, dust and other airborne particles as other types of sensors, such that infrared sensors are advantageous in situations in which it would otherwise be difficult to detect an object due to smoke, dust and/or other airborne particles, such as during a fire.
A specific example in which infrared sensors are utilized is in missile defense systems. For instance, a missile defense system utilizes an infrared sensor to detect heat associated with a missile in order to intercept the missile, such as by destroying the missile, before the missile hits its intended target.
The infrared sensors described above must be tested prior to utilizing the sensors to ensure that the sensors correctly detect the desired objects. In the example of a missile defense system, an infrared sensor is typically tested by projecting images of typical objects on a display and positioning the sensor to view the display. The sensor is then monitored to determine whether it accurately detects the image of the object. Thus, the projected images must be as realistic as possible to ensure that the sensor is being tested in a realistic environment. In the case of an infrared sensor for a missile defense system, therefore, the projected images of missiles must accurately depict the shape and temperature of an actual missile.
Conventional infrared image projectors or simulators are typically integrated circuits made of semi-conductor materials in which current is transmitted through resistors to produce heat and create an infrared image, i.e., heater-bump scene projectors. The heat emitted by the resistors, however, is not enough to simulate many extremely high-temperature objects, such as the plume of missiles, fires or the like. Thus, the conventional infrared image projectors can only simulate a limited portion of the infrared spectrum, that is that portion associated with objects having lower temperatures. Furthermore, in addition to being very expensive and time-consuming to build initially, it is also very expensive and time-consuming to make any adjustments to a conventional infrared image projector after it is initially built, such as adjustments to generate a larger image, because each integrated circuit is custom-built for a particular application and any such adjustment requires a new custom-built integrated circuit.
Another type of conventional infrared image projector utilizes an electron-beam to generate target images. The electron-beam therefore “draws” an image on a screen and a sensor views the image from the same side of the screen as the electron-beam source is located. There are, however, many disadvantages associated with the electron-beam infrared image projector. One disadvantage is that the electron-beam must propagate through a vacuum to the screen such that the image projector must provide a vacuum environment for the electron-beam, which adds to the cost and complicates the design of the image projector. In addition, because the sensor and the electron-beam source must be located on the same side of the screen, the design of the image projector and placement of the sensor is awkward and further complicated. Moreover, the screen upon which the electron-beam draws the image must be electrically conductive, which limits the materials of which the screen may be made such that the screen design is not flexible. The high voltage of the electron-beam that must be utilized to create infrared images with portions having relatively high temperatures also produces hazardous X-rays, which requires that the electron-beam image projector be extensively shielded.
Thus, conventional infrared image projectors are capable of generating a desired image, but not generating the desired temperature associated with one or more portions of the image when the temperature is extremely hot and/or when a relatively hot portion of the image is located adjacent to a relatively cool portion of the image. For example, the plume of a missile may reach temperatures around 1000 Kelvin, but the atmosphere around the plume is not nearly that hot. Because conventional infrared image projectors are not capable of generating an image having one or more portions at 1000 Kelvin, expensive test may be required, such as actual missile launches or engine tests to accurately test missile defense systems, which is expensive and time consuming.
As such, there is a need for an infrared image generator that is capable of providing infrared images with one or more portions having extremely high temperatures, such as around 1000 Kelvin, that are adjacent to relatively cool portions of the image. In addition, there is a need for an infrared image generator that is easy and safe to make, use and adjust, if needed and that has a design that is flexible and not complicated. Such an infrared image generator should also cost less and be less time-consuming than the conventional infrared image generators.